TABLE OF CONTENTS I. Introduction · Definition · History II. Implementing CDMA Technology III. Security Issue of CDMA Networks IV. Conclusion V. Reference I. Introduction
Definition According to the Christine Martz, Code Division Multiple Access also known as CDMA is a digital wireless transmission technology that allows many signals to travel on the same frequency. CDMA uses a spread spectrum technique which digitally transmitting data or voice over radio frequencies. Sounds are digitized and information is converts into data packets that are encoded with a unique identification code. All of the data packets will send over a spread range of radio frequencies to the end device. When end devices receive the data packets, it will reassemble the data packets and converts it back to the useful sound and information which understand by the end users. CDMA’s spread spectrum technique most uses in 2G and 3G network because it provides better capacity and performance which it signals is hard to detect and interference. History The first cellular network at the world is using analog radio transmission technologies such as AMPS (Advanced Mobile Phone System) and introduced in the early 1980s. The increasing of demand for cellular system, industry developed a new set of digital wireless technologies called TDMA (Time Division Multiple Access) and GSM (Global System for Mobile) to solve the limited capacity of analog networks. However, TDMA was being standardized and CDMA concept is being introduced at 1989. The founders of the CDMA, California-based Qualcomm realized that CDMA technology could be used in commercial cellular communications and make better than other technologies. The company tested the protocol in the San Diego area and one year later the company joined forces with NYNEX to test cell phone technology in New York City. By 1993, it was selected by the Telecommunications Industry of America trade group as a standard for digital cellular phone networks. The first CDMA networks were commercially launched in 1995 and provided 10 times more capacity than analog networks. Since then, CDMA has become the fastest-growing of all wireless technologies until now.
II. Implementing CDMA technology What technology? CDMA implementation such as the standard IS-95 comprises a physical layer. The modulation scheme commonly used QPSK which is stand for quandrature-phase shift keying to provide the lower end of data transfer speeds. Generally, the common frequency bands in the US and Korea are 825 to 849 MHz with channel spacing of 1.23 MHz. The standard data transfer rate of CDMA is 9.6 kbps to 115 kbps depending on which technology is being used. In order to differentiate the channels, CDMA uses a spreading code technique which means that it spreads the information contained a particular signal over a much greater bandwidth than the original signal. The signal is transmitted below the noise level and is received through a correlator for dispreading of the wanted signal. Next, the wanted signal is processed through a narrow bandpass filter to eliminate unwanted signal. The codes, one or zero sequences is used to differentiate signals are designed and generated at a much higher rate than the baseband information. This rate is referred as a chip rate rather than a bit rate. The relationship between them is shown below: Spreading factor = chip rate / data rate Who? When? Where? California-based Qualcomm is the developer for CDMA. In 1989, the company tested the protocol in the San Diego area. One year later, the company joined forces with NYNEX to test cell phone technology in New York City. By 1993, it was selected by the Telecommunications Industry of America trade group as a standard for digital cellular phone networks (2G). Later, Sprint PCs currently known as Sprint Nextel announced it would adopt CDMA for its network. Why? As you know, the world's first cellular networks were introduced in the early 1980s, using analog radio transmission technologies such as AMPS (Advanced Mobile Phone System). Within a few years, cellular systems began to hit a capacity ceiling as millions of new subscribers signed up for service, demanding increasingly airtime. Dropped calls and network busy signals became common in many areas. The industry developed a new set of digital wireless technologies called TDMA (Time Division Multiple Access) and GSM (Global System for Mobile) to accommodate more traffic within a limited amount of radio spectrum. TDMA and GSM used a time-sharing protocol to provide three to four times more capacity than analog systems. However, just as TDMA was being standardized, an even better solution was found in CDMA. How? Below is the step to implement CDMA CDMA takes an entirely different approach from TDMA. CDMA, after digitized data, spreads it out over the entire available bandwidth. Multiple calls are overlaid on each other on the channel, with each assigned a unique sequence code. It is known that CDMA is a form of spread spectrum, which means that the data is sent to-many frequencies for use at any time in the specified range. CDMA works on information data from several possible sources such as digitized voice or ISDN channels. The data rates can be vary. For instances, the systems work with 64 Kbits/sec data can accept input rates of 8,16, 32, or 64 Kbits/sec. On the other hand, inputs which are less than 64 Kbits/sec are padded with extra bits to bring them up to 64 Kbits/sec. For inputs of 8, 16, 32, or 64 Kbits/sec, the system applies Forward Error Correction (FEC) coding, which increase the bit rate twice to 128 Kbits/sec. The complex modulation scheme transmits two bits at a time, in two bit symbols. For inputs less than 64 Kbits/sec each symbol is repeated to bring the transmission rate up to 64 kilosysmbols/sec. Lastly, each channel base station generates a unique code that changes for every connection. The base station adds together all the coded transmissions for every subscriber. The subscriber unit correctly generates its own matching code and uses it to extract the appropriate signals. Thus, the pseudo-random code must be deterministic. The subscriber station must be able to independent generate the code that matches the base station code. Other than that, it must appear random to a listener without prior knowledge of the code such as statistical properties of sampled white noise. Besides, the cross-correlation between any two codes must be small and the code must have a long period. Purpose: The purposes of implementing CDMA are: i) To overcome strong intentional interference (jamming) ii) To hide the signal from the eavesdropper (covertness) Geographical scope: In order to obtain greater coverage for 2G, CDMA need to implement in strategically location. Before implement, coverage maps and tower locations need to be collected. It then compared data to the road network where people live and commute. Because mobility is a fundamental characteristic of 2G network, it is important to identify where population resides as well as how that population can could move (e.g., roads). In other words, some combination of populated areas and paths for movement were necessary coverage target for the 2G network. As a result, road path is the ideal location as it would capture both attributes: populated areas and path for movement. Traffic requirement: There are 2 classes in traffic requirement in CDMA which are real time and non real time. Real time traffic is also known as a conversational traffic, means audio and video calls, or streaming traffic. Each of them has a meaning of being one-sided and may also be buffered while transmitted, i.e. transmitted with delay. Hence, this is characterized by strict Qos requirements, which translate to a fixed duration or a predefined bit rate. If a Real time call does not get the service it wants, then the service will be rejected. Thus, the major performance metric here is the blocking probability, since Qos is otherwise guaranteed. Non-real time traffic, on the other hand, is what we call elastic, which means that the transmission rate freely adjusted. This refers to the transfer of documents, browsing through webpage, or to downloadable audio and video files. The main requirement of it is the time to make transfer. III. Security Issue of CDMA Networks CDMA systems have the 42-bit PN (Pseudo-Random Noise) Sequence called “Long Code” to scramble voice and data. On the forward link (network to mobile), data is scrambled at a rate of 19.2 Kilo symbols per second (Ksps) and on the reverse link (mobile to network), data is scrambled at a rate of 1.2288 Mega chips per second (Mcps). This is to form unique code channels for individual users in both directions of the communication channel. Because the signals of all calls in a coverage area are spread over the entire bandwidth, it creates a noise-like appearance to other mobiles or detectors in the network as a form of disguise, making the signal of any one call difficult to distinguish and decode. CDMA network security protocols rely on a 64-bit authentication key (A-Key) and the Electronic Serial Number (ESN) of the mobile. A random binary number called RANDSSD, which is generated in the Authentication Center, also plays a role in the authentication procedures. The A-Key is programmed into the mobile and is stored in the Authentication Center of the network. In addition to authentication, the A-Key is used to generate the sub-keys for voice privacy and message encryption. CDMA uses the CAVE (Cellular Authentication and Voice Encryption) algorithm to generate a 128-bit sub-key called Shared Secret Data (SSD). The A-Key, ESN and network supplied RANDSSD are the inputs to the CAVE that generates the SSD. The SSD is divided into two parts that are SSD_A and SSD_B. Each of the parts consists 64 bit of the 128 bit sub-key. SSD_A is in change in creating authentication signatures while SSD_B is in change in generating keys to encrypt voice and signaling messages. The SSD can be shared with roaming service providers to allow local authentication. A fresh SSD can be generated when a mobile return to the home network or roams to a different system. IV. Conclusion: It is undeniable that 2G provides many benefits for the cellular phone services. However, after the 3G being launched. 2G has lost its popularity and gradually replaced by 3G version. The future 3G versions of the technology include IS-20000 which applies CDMA2000 as its physical layer. This incorporates much higher transfer rates than the previous 2G version. GSM 3G/EDGE technology is being implemented using CDMA, and a special form of W-CDMA. These new physical layers will be competitive with each other and lesser known 3G solutions in regards to data transfer rates and spectral efficiency. V. References 1. http://www.birds-eye.net/definition/c/cdma-code_division_multiple_access.shtml 2. http://www.cdg.org/technology/index.asp 3. http://www.ee.iitb.ac.in/eesa/Techno-Journalism/prize-winning%20entries/1st_prize_CDMA_Technology_Rajeev_Yadav.pdf 4. http://www.ehow.com/about_4703392_define-cdma-cell-phone-technology.html 5. http://en.wikipedia.org/wiki2G 6. http://www.webopedia.com/TERM/C/CDMA.html 7. http://zone.ni.com/devzone/cda/tut/p/id/7107 8. http://72.14.235.132/search?q=cache:If60z8-y1RQJ:www.ctr.columbia.edu/~cylin/pub/cdma.ps+%2Bpurpose+of+is-95+in+cdma&hl=en&ct=clnk&cd=1&gl=my 9. http://72.14.235.132/search?q=cache:K4ixYHSgOxsJ:ftp://ftp-sop.inria.fr/maestro/retreat2005/Giannis.ppt+traffic+requirement+for+cdma&hl=en&ct=clnk&cd=2&gl=my 10. http://209.85.175.132/search?q=cache:-WZ4nDQ66PsJ:www.cdg.org/technology/cdma_technology/white_papers/cdma_1x_security_overview.pdf+security+CDMA&hl=en&ct=clnk&cd=3&gl=my
I. Introduction
· Definition
· History
II. Implementing CDMA Technology
III. Security Issue of CDMA Networks
IV. Conclusion
V. Reference
I. Introduction
Definition
According to the Christine Martz, Code Division Multiple Access also known as CDMA is a digital wireless transmission technology that allows many signals to travel on the same frequency.
CDMA uses a spread spectrum technique which digitally transmitting data or voice over radio frequencies. Sounds are digitized and information is converts into data packets that are encoded with a unique identification code. All of the data packets will send over a spread range of radio frequencies to the end device. When end devices receive the data packets, it will reassemble the data packets and converts it back to the useful sound and information which understand by the end users. CDMA’s spread spectrum technique most uses in 2G and 3G network because it provides better capacity and performance which it signals is hard to detect and interference.
History
The first cellular network at the world is using analog radio transmission technologies such as AMPS (Advanced Mobile Phone System) and introduced in the early 1980s. The increasing of demand for cellular system, industry developed a new set of digital wireless technologies called TDMA (Time Division Multiple Access) and GSM (Global System for Mobile) to solve the limited capacity of analog networks. However, TDMA was being standardized and CDMA concept is being introduced at 1989.
The founders of the CDMA, California-based Qualcomm realized that CDMA technology could be used in commercial cellular communications and make better than other technologies. The company tested the protocol in the San Diego area and one year later the company joined forces with NYNEX to test cell phone technology in New York City. By 1993, it was selected by the Telecommunications Industry of America trade group as a standard for digital cellular phone networks. The first CDMA networks were commercially launched in 1995 and provided 10 times more capacity than analog networks. Since then, CDMA has become the fastest-growing of all wireless technologies until now.
II. Implementing CDMA technology
What technology?
CDMA implementation such as the standard IS-95 comprises a physical layer. The modulation scheme commonly used QPSK which is stand for quandrature-phase shift keying to provide the lower end of data transfer speeds. Generally, the common frequency bands in the US and Korea are 825 to 849 MHz with channel spacing of 1.23 MHz. The standard data transfer rate of CDMA is 9.6 kbps to 115 kbps depending on which technology is being used.
In order to differentiate the channels, CDMA uses a spreading code technique which means that it spreads the information contained a particular signal over a much greater bandwidth than the original signal. The signal is transmitted below the noise level and is received through a correlator for dispreading of the wanted signal. Next, the wanted signal is processed through a narrow bandpass filter to eliminate unwanted signal. The codes, one or zero sequences is used to differentiate signals are designed and generated at a much higher rate than the baseband information. This rate is referred as a chip rate rather than a bit rate. The relationship between them is shown below:
Spreading factor = chip rate / data rate
Who? When? Where?
California-based Qualcomm is the developer for CDMA. In 1989, the company tested the protocol in the San Diego area. One year later, the company joined forces with NYNEX to test cell phone technology in New York City. By 1993, it was selected by the Telecommunications Industry of America trade group as a standard for digital cellular phone networks (2G). Later, Sprint PCs currently known as Sprint Nextel announced it would adopt CDMA for its network.
Why?
As you know, the world's first cellular networks were introduced in the early 1980s, using analog radio transmission technologies such as AMPS (Advanced Mobile Phone System).
Within a few years, cellular systems began to hit a capacity ceiling as millions of new subscribers signed up for service, demanding increasingly airtime. Dropped calls and network busy signals became common in many areas.
The industry developed a new set of digital wireless technologies called TDMA (Time Division Multiple Access) and GSM (Global System for Mobile) to accommodate more traffic within a limited amount of radio spectrum. TDMA and GSM used a time-sharing protocol to provide three to four times more capacity than analog systems. However, just as TDMA was being standardized, an even better solution was found in CDMA.
How?
Below is the step to implement CDMA
CDMA takes an entirely different approach from TDMA. CDMA, after digitized data, spreads it out over the entire available bandwidth. Multiple calls are overlaid on each other on the channel, with each assigned a unique sequence code. It is known that CDMA is a form of spread spectrum, which means that the data is sent to-many frequencies for use at any time in the specified range.
CDMA works on information data from several possible sources such as digitized voice or ISDN channels. The data rates can be vary. For instances, the systems work with 64 Kbits/sec data can accept input rates of 8,16, 32, or 64 Kbits/sec. On the other hand, inputs which are less than 64 Kbits/sec are padded with extra bits to bring them up to 64 Kbits/sec.
For inputs of 8, 16, 32, or 64 Kbits/sec, the system applies Forward Error Correction (FEC) coding, which increase the bit rate twice to 128 Kbits/sec. The complex modulation scheme transmits two bits at a time, in two bit symbols. For inputs less than 64 Kbits/sec each symbol is repeated to bring the transmission rate up to 64 kilosysmbols/sec.
Lastly, each channel base station generates a unique code that changes for every connection. The base station adds together all the coded transmissions for every subscriber. The subscriber unit correctly generates its own matching code and uses it to extract the appropriate signals. Thus, the pseudo-random code must be deterministic. The subscriber station must be able to independent generate the code that matches the base station code. Other than that, it must appear random to a listener without prior knowledge of the code such as statistical properties of sampled white noise. Besides, the cross-correlation between any two codes must be small and the code must have a long period.
Purpose:
The purposes of implementing CDMA are:
i) To overcome strong intentional interference (jamming)
ii) To hide the signal from the eavesdropper (covertness)
Geographical scope:
In order to obtain greater coverage for 2G, CDMA need to implement in strategically location. Before implement, coverage maps and tower locations need to be collected. It then compared data to the road network where people live and commute. Because mobility is a fundamental characteristic of 2G network, it is important to identify where population resides as well as how that population can could move (e.g., roads). In other words, some combination of populated areas and paths for movement were necessary coverage target for the 2G network. As a result, road path is the ideal location as it would capture both attributes: populated areas and path for movement.
Traffic requirement:
There are 2 classes in traffic requirement in CDMA which are real time and non real time. Real time traffic is also known as a conversational traffic, means audio and video calls, or streaming traffic. Each of them has a meaning of being one-sided and may also be buffered while transmitted, i.e. transmitted with delay. Hence, this is characterized by strict Qos requirements, which translate to a fixed duration or a predefined bit rate. If a Real time call does not get the service it wants, then the service will be rejected. Thus, the major performance metric here is the blocking probability, since Qos is otherwise guaranteed.
Non-real time traffic, on the other hand, is what we call elastic, which means that the transmission rate freely adjusted. This refers to the transfer of documents, browsing through webpage, or to downloadable audio and video files. The main requirement of it is the time to make transfer.
III. Security Issue of CDMA Networks
CDMA systems have the 42-bit PN (Pseudo-Random Noise) Sequence called “Long Code” to scramble voice and data. On the forward link (network to mobile), data is scrambled at a rate of 19.2 Kilo symbols per second (Ksps) and on the reverse link (mobile to network), data is scrambled at a rate of 1.2288 Mega chips per second (Mcps). This is to form unique code channels for individual users in both directions of the communication channel. Because the signals of all calls in a coverage area are spread over the entire bandwidth, it creates a noise-like appearance to other mobiles or detectors in the network as a form of disguise, making the signal of any one call difficult to distinguish and decode.
CDMA network security protocols rely on a 64-bit authentication key (A-Key) and the Electronic Serial Number (ESN) of the mobile. A random binary number called RANDSSD, which is generated in the Authentication Center, also plays a role in the authentication procedures. The A-Key is programmed into the mobile and is stored in the Authentication Center of the network. In addition to authentication, the A-Key is used to generate the sub-keys for voice privacy and message encryption.
CDMA uses the CAVE (Cellular Authentication and Voice Encryption) algorithm to generate a 128-bit sub-key called Shared Secret Data (SSD). The A-Key, ESN and network supplied RANDSSD are the inputs to the CAVE that generates the SSD. The SSD is divided into two parts that are SSD_A and SSD_B. Each of the parts consists 64 bit of the 128 bit sub-key. SSD_A is in change in creating authentication signatures while SSD_B is in change in generating keys to encrypt voice and signaling messages. The SSD can be shared with roaming service providers to allow local authentication. A fresh SSD can be generated when a mobile return to the home network or roams to a different system.
IV. Conclusion:
It is undeniable that 2G provides many benefits for the cellular phone services. However, after the 3G being launched. 2G has lost its popularity and gradually replaced by 3G version. The future 3G versions of the technology include IS-20000 which applies CDMA2000 as its physical layer. This incorporates much higher transfer rates than the previous 2G version. GSM 3G/EDGE technology is being implemented using CDMA, and a special form of W-CDMA. These new physical layers will be competitive with each other and lesser known 3G solutions in regards to data transfer rates and spectral efficiency.
V. References
1. http://www.birds-eye.net/definition/c/cdma-code_division_multiple_access.shtml
2. http://www.cdg.org/technology/index.asp
3. http://www.ee.iitb.ac.in/eesa/Techno-Journalism/prize-winning%20entries/1st_prize_CDMA_Technology_Rajeev_Yadav.pdf
4. http://www.ehow.com/about_4703392_define-cdma-cell-phone-technology.html
5. http://en.wikipedia.org/wiki2G
6. http://www.webopedia.com/TERM/C/CDMA.html
7. http://zone.ni.com/devzone/cda/tut/p/id/7107
8. http://72.14.235.132/search?q=cache:If60z8-y1RQJ:www.ctr.columbia.edu/~cylin/pub/cdma.ps+%2Bpurpose+of+is-95+in+cdma&hl=en&ct=clnk&cd=1&gl=my
9. http://72.14.235.132/search?q=cache:K4ixYHSgOxsJ:ftp://ftp-sop.inria.fr/maestro/retreat2005/Giannis.ppt+traffic+requirement+for+cdma&hl=en&ct=clnk&cd=2&gl=my
10. http://209.85.175.132/search?q=cache:-WZ4nDQ66PsJ:www.cdg.org/technology/cdma_technology/white_papers/cdma_1x_security_overview.pdf+security+CDMA&hl=en&ct=clnk&cd=3&gl=my